Accounts Payable, Accrued Expenses and Other Current Liabilities - Components of Accounts Payable, Accrued Expenses and Other Current Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounts Payable Accrued Expenses And Other Current Liabilities [Abstract]
Clinical and preclinical trials	$ 34,182	$ 25,150
Payroll and payroll-related	23,832	13,439
Accrued professional services and other current liabilities	9,379	6,368
Royalties payable	6,377	2,296
Accounts payable	3,290	2,073
Interest payable	1,698	1,698
Total	$ 78,758	$ 51,024